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ISL83088EIBZ-T 参数 Datasheet PDF下载

ISL83088EIBZ-T图片预览
型号: ISL83088EIBZ-T
PDF下载: 下载PDF文件 查看货源
内容描述: + -15kV的ESD保护, 5V,全故障保护,分数( 1/8 )机组负荷, RS - 485 / RS -422收发器 [+-15kV ESD Protected, 5V, Full Fail-Safe, Fractional (1/8) Unit Load, RS-485/RS-422 Transceivers]
分类和应用:
文件页数/大小: 18 页 / 828 K
品牌: INTERSIL [ Intersil ]
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ISL83080E, ISL83082E, ISL83083E, ISL83085E, ISL83086E, ISL83088E  
Receivers easily meet the data rates supported by the  
corresponding driver, and all receiver outputs are three-  
statable via the active low RE input.  
to an exposed port on the exterior of the finished product.  
Simply touching the port pins, or connecting a cable, can  
cause an ESD event that might destroy unprotected ICs.  
These new ESD structures protect the device whether or  
not it is powered up, protect without allowing any latchup  
mechanism to activate, and without degrading the RS-485  
common mode range of -7V to +12V. This built-in ESD  
protection eliminates the need for board level protection  
structures (e.g., transient suppression diodes), and the  
associated, undesirable capacitive load they present.  
Driver Features  
The RS-485/422 driver is a differential output device that  
delivers at least 1.5V across a 54load (RS-485), and at  
least 2V across a 100load (RS-422). The drivers feature  
low propagation delay skew to maximize bit width, and to  
minimize EMI.  
All drivers are three-statable via the active high DE input.  
Data Rate, Cables, and Terminations  
The 115kbps and 500kbps driver outputs are slew rate  
limited to minimize EMI, and to minimize reflections in  
unterminated or improperly terminated networks. Outputs of  
the ISL83086E, ISL83088E drivers are not limited, so faster  
output transition times allow data rates of at least 10Mbps.  
RS-485/422 are intended for network lengths up to 4000’,  
but the maximum system data rate decreases as the  
transmission length increases. Devices operating at 10Mbps  
are limited to lengths less than 100’, while the 115kbps  
versions can operate at full data rates with lengths of several  
thousand feet.  
Hot Plug Function  
When a piece of equipment powers up, there is a period of  
time where the processor or ASIC driving the RS-485 control  
lines (DE, RE) is unable to ensure that the RS-485 Tx and  
Rx outputs are kept disabled. If the equipment is connected  
to the bus, a driver activating prematurely during power up  
may crash the bus. To avoid this scenario, the ISL83080,  
ISL83082, ISL83083, ISL83085 versions incorporate a “Hot  
Twisted pair is the cable of choice for RS-485/422 networks.  
Twisted pair cables tend to pick up noise and other  
electromagnetically induced voltages as common mode  
signals, which are effectively rejected by the differential  
receivers in these ICs.  
Proper termination is imperative, when using the 10Mbps  
devices, to minimize reflections. Short networks using the  
115kbps versions need not be terminated, but, terminations  
are recommended unless power dissipation is an overriding  
concern.  
Plug” function. Circuitry monitoring V ensures that, during  
CC  
power up and power down, the Tx and Rx outputs remain  
disabled, regardless of the state of DE and RE, if V  
is less  
CC  
than ~3.4V. This gives the processor/ASIC a chance to stabilize  
and drive the RS-485 control lines to the proper states.  
In point-to-point, or point-to-multipoint (single driver on bus)  
networks, the main cable should be terminated in its  
characteristic impedance (typically 120) at the end farthest  
from the driver. In multi-receiver applications, stubs  
connecting receivers to the main cable should be kept as  
short as possible. Multipoint (multi-driver) systems require  
that the main cable be terminated in its characteristic  
impedance at both ends. Stubs connecting a transceiver to  
the main cable should be kept as short as possible.  
DI = V  
CC  
5
V
3.4V  
CC  
3.2V  
2.5  
0
5
2.5  
0
R
R
= 1kΩ  
= 1kΩ  
A/Y  
RO  
L
L
Built-In Driver Overload Protection  
ISL83080E  
As stated previously, the RS-485 spec requires that drivers  
survive worst case bus contentions undamaged. These  
devices meet this requirement via driver output short circuit  
current limits, and on-chip thermal shutdown circuitry.  
5
2.5  
ISL83080E  
The driver output stages incorporate short circuit current  
limiting circuitry which ensures that the output current never  
exceeds the RS-485 spec, even at the common mode  
voltage range extremes. Additionally, these devices utilize a  
foldback circuit which reduces the short circuit current, and  
thus the power dissipation, whenever the contending voltage  
exceeds either supply.  
0
TIME (40µs/DIV)  
FIGURE 7. HOT PLUG PERFORMANCE (ISL83080E) vs  
DEVICE WITHOUT HOT PLUG CIRCUITRY  
(ISL83086E)  
ESD Protection  
In the event of a major short circuit condition, devices also  
include a thermal shutdown feature that disables the drivers  
whenever the die temperature becomes excessive. This  
eliminates the power dissipation, allowing the die to cool. The  
drivers automatically re-enable after the die temperature  
drops about 15 degrees. If the contention persists, the thermal  
shutdown/re-enable cycle repeats until the fault is cleared.  
Receivers stay operational during thermal shutdown.  
All pins on these devices include class 3 Human Body  
Model (HBM) ESD protection structures, but the RS-485  
pins (driver outputs and receiver inputs) incorporate  
advanced structures allowing them to survive ESD events  
in excess of ±15kV HBM. The RS-485 pins are particularly  
vulnerable to ESD damage because they typically connect  
FN6085.6  
11  
September 12, 2005  
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